EMI filter for plasma display panel

ABSTRACT

A plasma display panel (PDP) includes an EMI filter at a front portion thereof for blocking/shielding substantial amounts of electromagnetic waves. The filters has high visible transmission, and is capable of blocking/shielding electromagnetic waves. In certain example embodiments, a silver based coating of the EMI filter reduces damage from EMI radiation through highly conductive Ag layers, blocks significant amounts of NIR and IR radiation from outdoor sunlight to reduce PDP panel temperature, and enhances contrast ratio through reduced reflection, while maintaining high visible transmission. In certain example embodiments, at least one layer of or including silicon nitride may be Si-rich, and/or at least one layer including an oxide of Ni and/or Cr may be a suboxide, in order to improve heat treatability of the coated article.

This application is a Continuation of application Ser. No. 12/659,912,filed Mar. 25, 2010, now U.S. Pat. No. 7,931,971, which is aContinuation of Ser. No. 12/230,033, filed Aug. 21, 2008 (now U.S. Pat.No. 7,713,633), and which claims benefit of Provisional 61/071,936,filed May 27, 2008, the entire contents of which are all herebyincorporated herein by reference in this application.

This invention relates to a plasma display panel (PDP) including afilter at a front portion thereof for blocking/shielding substantialamounts of electromagnetic waves. The filter has high visibletransmission, and is capable of blocking/shielding electromagneticwaves.

BACKGROUND OF THE INVENTION

Image display devices are being widely used in a variety ofapplications, including TV screens, monitors of personal computers, etc.The plasma display panel (PDP) is gaining popularity as anext-generation display device to replace the CRT because a PDP is thinand a large screen can be readily fabricated with a plurality of units.A PDP includes a plasma display panel on which an image is displayedusing a gas discharge phenomenon, and exhibits superior displaycapabilities, including high display capacity, high brightness, highcontrast, clear latent image, a wide viewing angle, etc. In a PDPapparatus, when a direct current (DC) or alternating current (AC)voltage is applied to electrodes, a discharge of gas plasma is created,resulting in the emission of ultraviolet (UV) light. The UV emissionexcites adjacent phosphor materials, resulting in electromagneticemission of visible light. Despite the above advantages, PDPs faceseveral challenges associated with driving characteristics, including anincrease in electromagnetic wave radiation, near-infrared emission, andphosphor surface reflection, and an obscured color purity due to orangelight emitted from helium (He), neon, or xenon (Xe) used as a sealinggas.

Some believe that the electromagnetic waves and near-infrared raysgenerated in PDPs may adversely affect human bodies and causemalfunctions of precision machines such as wireless telephones or remotecontrollers (e.g., see US 2006/0083938, incorporated herein byreference). These waves, taken individually or collectively, may bereferred to as electromagnetic interference (EMI). Thus, in order tomake use of such PDPs, there is a desire to reduce the electromagneticwaves and near-infrared (IR or NIR) rays emitted from the PDPs to apredetermined level or less. In this respect, various PDP filters havebeen proposed for shielding electromagnetic waves or near-infrared raysemitted from the PDPs, reducing reflection of light and/or enhancingcolor purity. The proposed PDP filters are also required to meettransmittance requirements because the filters are installed on a frontsurface of each of the PDPs.

In order to reduce the electromagnetic waves and NIR waves emitted fromplasma display panels to a predetermined level or less, various PDPfilters have been used for the purposes of e.g., shieldingelectromagnetic waves or NIR emitted from the PDPs, reducing reflectionof light and/or enhancing color purity. High transmittance is requiredfor such filters because they are generally applied to the front surfaceof PDPs. Typical electromagnetic wave shielding filters meeting suchrequirements and characteristics are classified into a metalmesh-pattern filter and a transparent conductive film filter. Althoughthe metal mesh-pattern filter exhibits a good electromagnetic waveshielding effect, it has several disadvantages including poortransmittance, image distortion, and an increase in the production costdue to a costly mesh. Due to such disadvantages, electromagnetic waveshielding filters using transparent conductive films using indium tinoxide (ITO) are being widely used instead of the metal mesh-patternfilter. The transparent conductive film is generally formed of amulti-level thin film structure in which a metal film and ahigh-refractive-index transparent thin layer are sandwiched. Silver or asilver-based alloy may be used as the metal film. However, conventionPDP EMI filters tend to lack durability and/or can stand to be improvedupon with respect to visible transmission and/or shielding properties.

Moreover, certain PDP EMI filters need to be heat treated (e.g.,thermally tempered). Such heat treatment typically requires use oftemperature(s) of at least 580 degrees C., more preferably of at leastabout 600 degrees C. and still more preferably of at least 620 degreesC. The terms “heat treatment” and “heat treating” as used herein meanheating the article to a temperature sufficient to achieve thermaltempering and/or heat strengthening of the glass inclusive article. Thisdefinition includes, for example, heating a coated article in an oven orfurnace at a temperature of least about 580 degrees C., more preferablyat least about 600 degrees C., for a sufficient period to allowtempering and/or heat strengthening. In certain instances, the HT may befor at least about 4 or 5 minutes. The use of such high temperatures(e.g., for 5-10 minutes or more) often causes coatings to break downand/or causes one or more of the aforesaid desirable characteristics tosignificantly deteriorate in an undesirable manner. Conventional PDP EMIfilters tend to suffer from a lack of thermal stability and/ordurability upon heat treatment (HT). In particular, heat treatment tendsto cause conventional PDP filters to break down.

In view of the above, there exists a need in the art for an improved PDPfilter which is improved (with respect to conventional PDP EMI filters)with respect to one or more of: (i) improved chemical durability, (ii)improved thermal stability (e.g., upon optional heat treatment such astempering), (iii) improved visible transmission, and/or (iv) improvedEMI shielding properties.

BRIEF SUMMARY OF EXAMPLE EMBODIMENTS OF THE INVENTION

In certain example embodiments of this invention, a plasma display panel(PDP) includes a filter at a front portion thereof forblocking/shielding substantial amounts of electromagnetic waves. Thefilters has high visible transmission, and is capable ofblocking/shielding electromagnetic waves. In certain exampleembodiments, a silver based coating of the EMI filter reduces damagefrom EMI radiation through highly conductive Ag layers, blockssignificant amounts of NIR and IR radiation from outdoor sunlight toreduce PDP panel temperature, and enhances contrast ratio throughreduced reflection, while maintaining high visible transmission.

In certain example embodiments of this invention, there is provided aplasma display device comprising: a plasma display panel (PDP); anelectromagnetic interference (EMI) filter provided at a front portion ofthe plasma display panel, the EMI filter including an EMI coatingsupported by a glass substrate, the EMI coating including the followinglayers moving away from the glass substrate: a first layer comprisingsilicon nitride; a first high index layer having a refractive index (n)of at least about 2.2; a first layer comprising zinc oxide; a first EMIshielding layer, comprising silver contacting the first layer comprisingzinc oxide; a first layer comprising an oxide of Ni and/or Cr contactingthe first EMI shielding layer comprising silver; a first metal oxidelayer; a second layer comprising zinc oxide; a second EMI shieldinglayer comprising silver contacting the second layer comprising zincoxide; a second layer comprising an oxide of Ni and/or Cr contacting thesecond EMI shielding layer comprising silver; a second metal oxidelayer; a third layer comprising zinc oxide; a third EMI shielding layercomprising silver contacting the third layer comprising zinc oxide; athird layer comprising an oxide of Ni and/or Cr contacting the third EMIshielding layer comprising silver; a third metal oxide layer; and anovercoat layer.

In other example embodiments of this invention, there is provided EMIfilter for a display device, the EMI filter comprising: an EMI coatingsupported by a glass substrate, the EMI coating including the followinglayers moving away from the glass substrate: a first layer comprisingzinc oxide; a first EMI shielding layer comprising silver contacting thefirst layer comprising zinc oxide; a first layer comprising an oxide ofNi and/or Cr contacting the first EMI shielding layer comprising silver;a second layer comprising zinc oxide; a second EMI shielding layercomprising silver contacting the second layer comprising zinc oxide; asecond layer comprising an oxide of Ni and/or Cr contacting the secondEMI shielding layer comprising silver; a third layer comprising zincoxide; a third EMI shielding layer comprising silver contacting thethird layer comprising zinc oxide; a third layer comprising an oxide ofNi and/or Cr contacting the third EMI shielding layer comprising silver;and an overcoat layer; wherein the third EMI shielding layer comprisingsilver is thicker than the first and/or second EMI shielding layerscomprising silver.

plasma display device comprising: a plasma display panel; anelectromagnetic interference (EMI) filter provided at a front portion ofthe plasma display panel, the EMI filter including an EMI coatingsupported by a glass substrate; the EMI coating including the followinglayers moving away from the glass substrate: a first layer comprisingsilicon nitride; a first layer comprising zinc oxide; a first EMIshielding layer comprising silver contacting the first layer comprisingzinc oxide; a first layer comprising an oxide of Ni and/or Cr contactingthe first EMI shielding layer comprising silver; a first metal oxidelayer; a second layer comprising zinc oxide; a second EMI shieldinglayer comprising silver contacting the second layer comprising zincoxide; a second layer comprising an oxide of Ni and/or Cr contacting thesecond EMI shielding layer comprising silver; a second metal oxidelayer; a third layer comprising zinc oxide; a third EMI shielding layercomprising silver contacting the third layer comprising zinc oxide; athird layer comprising an oxide of Ni and/or Cr contacting the third EMIshielding layer comprising silver; a third metal oxide layer; anovercoat layer; and wherein the third layer comprising an oxide of Niand/or Cr is less oxided than is/are one or both of the first and/orsecond layers comprising an oxide of Ni and/or Cr.

In certain example embodiments, the first layer comprising siliconnitride comprises Si_(x)N_(y) layer(s), where x/y is from 0.76 to 1.5(more preferably from about 0.85 to 1.2).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) is a cross sectional view of an EMI filter for a displaypanel (e.g. PDP panel) according to an example embodiment of thisinvention.

FIG. 1( b) is a cross sectional view of a PDP panel including an EMIfilter (e.g., the filter of any embodiment herein) according to anexample embodiment of this invention.

FIG. 2 is a transmission/reflectance vs. wavelength graph illustratingoptical characteristics of the filter of FIG. 1( a) according to anexample embodiment of this invention.

FIG. 3 is a cross sectional view of an EMI filter for a display panel(e.g. PDP panel) according to another example embodiment of thisinvention.

FIG. 4 is a listing of the layers of an EMI filter for a display panel(e.g. PDP panel) according to another example embodiment of thisinvention.

FIG. 5 is a listing of the layers of an example antireflection (AR)coating which may optionally be used in conjunction with an EMI coatingin certain example embodiments of this invention.

FIG. 6 is a cross sectional view of the EMI filter (TCC) (of anyembodiment of this invention), front cover glass, and optional ARcoating for use at the front of a PDP panel according to an exampleembodiment of this invention.

FIG. 7 is a cross sectional view of the EMI filter (TCC) (of anyembodiment of this invention), front cover glass, and a pair of optionalAR coatings for use at the front of a PDP panel according to anotherexample embodiment of this invention.

FIG. 8 is a cross sectional view of the EMI filter (TCC) (of anyembodiment of this invention), front cover glass, and a pair of optionalAR coatings for use at the front of a PDP panel according to anotherexample embodiment of this invention.

FIG. 9 is a table listing example optical characteristics of filterstructures of certain example embodiments of this invention.

FIG. 10 is a transmission (T)/reflectance (R) vs. wavelength graphillustrating optical characteristics of the filters according to variousexample embodiments of this invention.

FIG. 11 is a graph illustrating normalized absorption spectrum ofexample optional pink dye which may be used in certain exampleembodiments of this invention.

FIG. 12 is a table listing example optical characteristics of filterstructures of certain example embodiments of this invention whichinclude the use of dye.

FIG. 13 is a transmission (T)/reflectance (R) vs. wavelength graphillustrating optical characteristics of the filters according to variousexample embodiments of this invention which include the use of dye.

FIG. 14 is a cross sectional view of an EMI filter for a display panel(e.g. PDP panel) according to another example embodiment of thisinvention.

FIG. 15 is a cross sectional view of an EMI filter for a display panel(e.g. PDP panel) according to another example embodiment of thisinvention.

FIG. 16 is a cross sectional view of an EMI filter for a display panel(e.g. PDP panel) according to another example embodiment of thisinvention.

FIG. 17 is a cross sectional view of an EMI filter for a display panel(e.g. PDP panel) according to another example embodiment of thisinvention.

FIG. 18 is a cross sectional view of an EMI filter for a display panel(e.g. PDP panel) according to another example embodiment of thisinvention.

FIG. 19 is a cross sectional view of an EMI filter for a display panel(e.g. PDP panel) according to another example embodiment of thisinvention.

DETAILED DESCRIPTION OF EXAMPLES OF THE INVENTION

Referring now more particularly to the accompanying drawings in whichlike reference numerals indicate like parts/layers throughout theseveral views.

A plasma display panel (PDP) includes a filter at a front portionthereof for blocking/shielding substantial amounts of electromagneticwaves. The filter has high visible transmission, and is capable ofblocking/shielding substantial portions of electromagnetic waves.Certain example embodiments of this invention relate to an Ag-basedmultiple layered transparent conductive coating (TCC) for displayapplications (e.g., PDP applications). This EMI filter coating includesthree or more Ag based layers sandwiched between metal oxides, nitridesor oxynitrides. It provides the functions of blocking EMI radiation andminimizing/reducing near infrared and infrared transmissions. The Agbased transparent conductive coating can be manufactured by magnetronsputtering on glass in certain example embodiments. The coating on glassmay go through a post heat-treatment in a typical oven or temperingfurnace to enhance glass strength and increase coating conductivity andtransparency in certain example embodiments (i.e., heat treatment). Incertain example embodiments, the Ag-based TCC (or EMI filter) coatingincludes or consists of four layers of ZnOx/Ag/NiCrOx sandwiched betweenmetal oxides and nitrides. In certain example embodiments, the metaloxides (e.g., tin oxide, zinc oxide) and nitrides (e.g., siliconnitride) used have refractive indices (n) in visible higher than 1.8,and can be nonconductive such as SiNx or conductive such as ZnAlOx. Incertain example embodiments, certain of the materials (e.g., Ag, zincoxide based layers, and NiCrOx based layers) are the same for all threeor four stacks, but the thickness of the dielectric and Ag layers areadjusted to meet the sheet resistance and optics targets for each of thelayer stacks. Moreover, other layers may differ from stack to stack inorder to enhance durability and optical performance. In certain exampleembodiments, the EMI filter may also include a conductive frit framearound the periphery to provide a low conductance contact to the housingof the plasma TV. The completed filter may also include AR coating filmlaminated to the front surface to reduce display reflectance and alaminate with a purple and/or pink dye attached to the back of thecoated glass to improve color performance of the plasma TV.

FIG. 1( a) is a cross sectional view of an EMI filter for use in a PDPpanel (or other type of display panel) according to an exampleembodiment of this invention. FIG. 1( b) is a cross sectional viewillustrating the filter of FIG. 1( a) on a PDP panel. As shown in FIG.1( b), the filter of FIG. 1( a) is provided on the interior side (sidefacing away from the sun) of a front cover glass substrate at the frontof the PDP. The EMI filters according to example embodiments of thisinvention may or may not be used in conjunctions with antireflection(AR) coatings. An AR coating may be provided on the cover glass, on theopposite or the same side as the EMI filter coating. The PDP panel 40shown in FIG. 1( b) may be any suitable type of PDP panel. Example PDPpanels are described in US 2006/0083938 (e.g., see FIG. 6), the entiretyof which is incorporated herein by reference. For purposes of example,the FIG. 1( a) filter structure may be used in place of 100 or 100′ inthe PDP device of FIG. 6 of US 2006/0083938, as an example applicationof this invention.

The EMI filter structure of FIG. 1 includes cover glass substrate 1(e.g., clear, green, bronze, or blue-green glass substrate from about1.0 to 10.0 mm thick, more preferably from about 1.0 mm to 3.5 mmthick), and EMI filter coating (or layer system) 30 provided on thesubstrate 1 either directly or indirectly. The coating (or layer system)30 includes: dielectric silicon nitride base layer 3 which may be Si₃N₄,of the Si-rich type for haze reduction, or of any other suitablestoichiometry in different embodiments of this invention, high indextitanium oxide inclusive layer 4, first lower contact layer 7 (whichcontacts conductive EMI shielding layer 9), first conductive andpreferably metallic EMI shielding layer 9, first upper contact layer 11(which contacts layer 9), dielectric or conductive metal oxide layer 13(which may be deposited in one or multiple steps in differentembodiments of this invention), second lower contact layer 17 (whichcontacts EMI shielding layer 19), second conductive and preferablymetallic EMI shielding layer 19, second upper contact layer 21 (whichcontacts layer 19), dielectric or conductive metal oxide layer 23,dielectric silicon nitride based layer(s) 25, 26 which may be Si₃N₄, ofthe Si-rich type for haze reduction, or of any other suitablestoichiometry in different embodiments of this invention, second highindex titanium oxide inclusive layer 24, third lower contact layer 27(which contacts conductive EMI shielding layer 29), third conductive andpreferably metallic EMI shielding layer 29, third upper contact layer 31(which contacts layer 29), dielectric or conductive metal oxide layer 33(which may be deposited in one or multiple steps in differentembodiments of this invention), fourth lower contact layer 37 (whichcontacts EMI shielding layer 39), fourth conductive and preferablymetallic EMI shielding layer 39, fourth upper contact layer 41 (whichcontacts layer 39), dielectric or conductive metal oxide layer 43, andprotective overcoat layer 45 of or including silicon nitride or thelike. The “contact” layers 7, 11, 17, 21, 27, 31, 37 and 41 each contactat least one EMI shielding/reflecting layer (e.g., layer based on Ag)(9, 19, 29, 39). The aforesaid layers 3-45 make up the EMI shieldingcoating 30 which is provided on substrate 1 for blocking substantialamounts of EMI from being emitted from the PDP device. Example sheetresistances are 0.8, 1.2 and 1.6 ohm/sq. for the coatings 30 indifferent example embodiments. In certain example embodiments, thecoating 30 may have a sheet resistance of from about 0.5 to 1.8 ohms/sq.

An alternative (not shown) to the FIG. 1 embodiment involves splittingeach of metal oxide layers 13 and 33 into two different layers andprovided a silicon nitride based layer in between the split layers. Inother words, for example, tin oxide based layer 13 would be replacedwith a first tin oxide based layer 13′, a silicon nitride layer 13″ anda second tin oxide based layer 13′″. Likewise, tin oxide based layer 33would be replaced with a first tin oxide based layer 33′, a siliconnitride layer 33″ and a second tin oxide based layer 33′″. Thisalternative layer stack is particularly advantageous with respect toheat treated and heat treatable filters that may be used when, forexample, bus bar/black frit is applied on top of the coating 30. In suchembodiments, the use of the NiCrOx material for layers 11, 21, 31 and 41is advantageous in that it is more durable and provides for betterthermal stability compared to other possible materials such as zincoxide or zinc aluminum oxide.

Dielectric layers 3, 25, 26 and 45 preferably have a refractive index(n) of from about 1.9 to 2.1, more preferably from about 1.97 to 2.08,and may be of or include silicon nitride in certain embodiments of thisinvention. Silicon nitride layers 3, 3 a, 25, 26 and 45 may, among otherthings, improve heat-treatability of the coated articles, e.g., such asthermal tempering or the like. The silicon nitride of one, two or all ofthese layers may be of the stoichiometric type (Si₃N₄) type, oralternatively of the Si-rich type in different embodiments of thisinvention. For example, Si-rich silicon nitride 3, 3 a, 26 combined withzinc oxide inclusive layer 7 (and/or 27) under a silver based EMIshielding layer 9 (and/or 29) may permit the silver to be deposited(e.g., via sputtering or the like) in a manner which causes its sheetresistance to be lessened compared to if certain other material(s) wereunder the silver (and thus, EMI shielding to be improved). Moreover, thepresence of free Si in a Si-rich silicon nitride inclusive layer 3and/or 3 a may allow certain atoms such as sodium (Na) which migrateoutwardly from the glass 1 during HT to be more efficiently stopped bythe Si-rich silicon nitride inclusive layer before they can reach thesilver and damage the same. Thus, it is believed that the oxidationcaused by heat treatment allows visible transmission to increase, andthat the Si-rich Si_(x)N_(y) can reduce the amount of damage done to thesilver layer(s) during HT in certain example embodiments of thisinvention thereby allowing sheet resistance (R_(s)) to decrease in asatisfactory manner and EMI shielding to be improved. In certain exampleembodiments, when Si-rich silicon nitride us used in layer(s) 3, 3 a,and/or 25, 26, the Si-rich silicon nitride layer as deposited may becharacterized by Si_(x)N_(y) layer(s), where x/y may be from 0.76 to1.5, more preferably from 0.8 to 1.4, still more preferably from 0.85 to1.2. Moreover, in certain example embodiments, before and/or after HTthe Si-rich Si_(x)N_(y) layer(s) (e.g., 3 and/or 3 a) may have an indexof refraction “n” of at least 2.05, more preferably of at least 2.07,and sometimes at least 2.10 (e.g., 632 nm) (note: stoichiometric Si₃N₄which may also be used has an index “n” of 2.02-2.04). In certainexample embodiments, it has surprisingly been found that improvedthermal stability is especially realizable when the Si-rich Si_(x)N_(y)layer(s) as deposited has an index of refraction “n” of at least 2.10,more preferably of at least 2.2, and most preferably from 2.2 to 2.4.Also, the Si-rich Si_(x)N_(y) layer in certain example embodiments mayhave an extinction coefficient “k” of at least 0.001, more preferably ofat least 0.003 (note: stoichiometric Si₃N₄ has an extinction coefficient“k” of effectively 0). Again, in certain example embodiments, it hassurprisingly been found that improved thermal stability can be realizedwhen “k” for the Si-rich Si_(x)N_(y) layer is from 0.001 to 0.05 asdeposited (550 nm). It is noted that n and k tend to drop due to heattreatment. Any and/or all of the silicon nitride layers (3, 25, 26, 45)discussed herein may be doped with other materials such as stainlesssteel or aluminum in certain example embodiments of this invention. Forexample, any and/or all silicon nitride layers discussed herein mayoptionally include from about 0-15% aluminum, more preferably from about1 to 10% aluminum, most preferably from 1-4% aluminum, in certainexample embodiments of this invention. The silicon nitride may bedeposited by sputtering a target of Si or SiAl in certain embodiments ofthis invention. These layers are provided in order to improve thereflection of EMI without sacrificing visible transmission.

High index layers 4 and 24 are preferably of or including an oxide oftitanium (e.g., TiO₂, or other suitable stoichiometry) in certainexample embodiments of this invention. Layers 4 and 24 preferably have arefractive index (n) of at least about 2.2, more preferably of at leastabout 2.3, 2.4 or 2.45, in certain example embodiments of thisinvention. These layers 4 and 24 may be conductive or dielectric indifferent example embodiments of this invention. These layers areprovided in order to improve the reflection of EMI without sacrificingvisible transmission.

EMI shielding/reflecting layers 9, 19, 29 and 39 are preferablysubstantially or entirely metallic and/or conductive, and may compriseor consist essentially of silver (Ag), gold, or any other suitable EMIreflecting material. EMI shielding layers 9, 19, 29 and 39 help allowthe coating to have good conductivity and block EMI from being emittedfrom the PDP panel. It is possible for these layers to be slightlyoxidized in certain embodiments of this invention.

The upper contact layers 11, 21, 31 and 41 may be of or include nickel(Ni) oxide, chromium/chrome (Cr) oxide, or a nickel alloy oxide such asnickel chrome oxide (NiCrO_(x)), or other suitable material(s), incertain example embodiments of this invention. The use of, for example,NiCrO_(x) in these layers allows durability to be improved. TheNiCrO_(x) of layers 11 and/or 21 may be fully oxidized in certainembodiments of this invention (i.e., fully stoichiometric), oralternatively may only be partially oxidized. In certain instances, theNiCrO_(x) layers may be at least about 50% oxidized. These layers (e.g.,of or including an oxide of Ni and/or Cr) may or may not be oxidationgraded in different embodiments of this invention. Oxidation gradingmeans that the degree of oxidation in the layer changes throughout thethickness of the layer so that for example a contact layer may be gradedso as to be less oxidized at the contact interface with the immediatelyadjacent IR reflecting layer than at a portion of the contact layer(s)further or more/most distant from the immediately adjacent IR reflectinglayer, and these contact layers may or may not be continuous indifferent embodiments of this invention across the entire IR reflectinglayer. The use of the NiCrOx material for one, two, three or all oflayers 11, 21, 31 and 41 is advantageous in that it is more durable andprovides for better thermal stability compared to other possiblematerials such as zinc oxide or zinc aluminum oxide. This is especiallythe case with respect to heat treated and heat treatable filters thatmay be used when, for example, bus bar/black frit is applied on top ofthe coating 30 in certain applications.

Metal oxide layers 13, 23, 33 and 43 may be of or include tin oxide incertain example embodiments of this invention. These layers preferablyhave a refractive index (n) of from about 1.9 to 2.1 in certain exampleembodiments of this invention, more preferably from about 1.95 to 2.05.These layers may be doped with other material such as zinc in certaininstances. However, as with other layers herein, other materials may beused in different instances. These layers are provided in order toimprove the reflection of EMI without sacrificing visible transmission.

Lower contact layers 7, 17, 27 and 37 in certain embodiments of thisinvention are of or include zinc oxide (e.g., ZnO). The zinc oxide ofthese layers may contain other materials as well such as Al (e.g., toform ZnAlO_(x)). For example, in certain example embodiments of thisinvention, one or more of these zinc oxide layers may be doped with fromabout 1 to 10% Al, more preferably from about 1 to 5% Al, and mostpreferably about 2 to 4% Al. The use of zinc oxide under the silver 9,19, 29, 39 allows for an excellent quality of silver to be achievedthereby improving conductivity and improving EMI shielding.

Other layer(s) below or above the illustrated coating may also beprovided. Thus, while the layer system or coating is “on” or “supportedby” substrate 1 (directly or indirectly), other layer(s) may be providedtherebetween. Thus, for example, the coating of FIG. 1 may be considered“on” and “supported by” the substrate 1 even if other layer(s) areprovided between layer 3 and substrate 1. Moreover, certain layers ofthe illustrated coating may be removed in certain embodiments, whileothers may be added between the various layers or the various layer(s)may be split with other layer(s) added between the split sections inother embodiments of this invention without departing from the overallspirit of certain embodiments of this invention.

In certain example embodiments of this invention, the Ag-based EMIshielding layers in the coating have different thicknesses. This is bydesign, and is particularly advantageous. The different thicknesses ofthe silver based layers 9, 19, 29, 39 are optimized to obtain a lowvisible reflection as seen from outside of the PDP apparatus (i.e., fromthe glass side of the film, in most embodiments, namely when the coating30 is on the interior surface of the substrate 1 facing the plasma), andat the same time permitting high visible transmittance. Silver layersburied deeper in the stack (i.e., further from the plasma) are masked toa certain extent by the absorption in the preceeding layers; therefore,they can be made thicker to improve EMI shielding without adverselyaffecting outside reflectance to any significant extent. Thus, thethickness (physical thickness) of a silver based EMI shielding layer(s)(e.g., 39) further from the plasma of the PDP panel can be significantlythicker than the thickness of a silver based EMI shielding layer(s)(e.g., 9) closer to the plasma of the PDP panel. The total silverthickness is unevenly distributed across the coating 30 in order to takeadvantageous of this effect. The total thickness of all silver basedlayers (9, 19, 29, 39) combined may be from about 25-80 nm in certainexample embodiments of this invention, more preferably from about 30-70nm, whereas the total thickness of the entire coating 30 may be fromabout 300 to 400 nm, more preferably from about 325 to 380 nm, and mostpreferably from about 330 to 375 in certain example embodiments of thisinvention. In certain example embodiments, the thickness (physicalthickness) of a silver based EMI shielding layer(s) (e.g., 39 or 29)further from the plasma of the PDP panel is at least about 1 nm thicker(more preferably at least about 2 nm thicker, and possibly at leastabout 3 or 4 nm thicker) than the thickness of a silver based EMIshielding layer(s) (e.g., 9) closer to the plasma of the PDP panel.

FIG. 2 is a transmission/reflectance vs. wavelength graph illustratingoptical characteristics of the filter of FIG. 1( a) when designed for asheet resistance of 0.8 ohms/square, thereby having thick silverlayer(s). In FIG. 2, T stands for transmission, G stands for glass sidereflectance, and F stands for film side reflectance. It can be seen inFIG. 2 that film side (i.e., the side closest to the plasma) reflectanceof EMI such as NIR is enhanced (much reflectance) while visibletransmission (e.g., from 450-650 nm) is kept high. This provides for afilter having good/high visible transmission, but muchreflectance/absorption in the NIR region where undesirable wavelengthsare present. In certain example embodiments, the combination of thecoating 30 and the substrate 1 have a visible transmission of at leastabout 50%, more preferably of at least about 55%, 58% or 60% in certainexample embodiments of this invention.

FIG. 3 is a cross sectional view of an EMI filter for a display panel(e.g. PDP panel) according to another example embodiment of thisinvention. The FIG. 3 embodiment is the same as the FIG. 1( a)-(b)embodiment discussed above, except that certain thicknesses aredifferent because the FIG. 3 filter is designed for a higher sheetresistance (Rs of 1.64 ohms/square).

While various thicknesses and materials may be used in layers indifferent embodiments of this invention, example thicknesses andmaterials for the respective layers on the glass substrate 1 in the FIG.1-3 embodiments are as follows, from the glass substrate outwardly:

Example Materials/Thicknesses; FIG. 1-3 Emobodiment Layer GlassPreferred Range More Preferred (1-10 mm thick) (nm) (nm) Example (nm)Si_(x)N_(y) (layer 3) 4-30 8-15 10-14 TiO_(x) (layer 4) 4-35 8-20 15ZnO_(x) (layer 7) 4-22 5-15 10 Ag (layer 9) 4-20 6-15  8-13 NiCrO_(x)(layer 11) 0.3-4   0.5-2    1 SnO₂ (layer 13) 10-100 25-90  55-80ZnO_(x) (layer 17) 4-22 5-15 10 Ag (layer 19) 4-24 6-20  8-18 NiCrO_(x)(layer 21) 0.3-4   0.5-2    1 SnO₂ (layer 23) 4-25 6-20 10-14 Si₃N₄(layer 25) 10-50  12-40  15-25 Si_(x)N_(y) (layer 26) 4-30 8-15 10-14TiO_(x) (layer 24) 4-35 8-20 15 ZnO_(x) (layer 27) 4-22 5-15 10 Ag(layer 29) 8-30 10-24  12-22 NiCrO_(x) (layer 31) 0.3-4   0.5-2    1SnO₂ (layer 33) 10-100 25-90  55-80 ZnO_(x) (layer 37) 4-22 5-15 10 Ag(layer 39) 8-30 10-24  11-20 NiCrO_(x) (layer 41) 0.3-4   0.5-2    1SnO₂ (layer 43) 4-25 6-20 10-18 Si₃N₄ (layer 45) 10-50  15-40  18-32

In another example embodiment of this invention, FIG. 4 describes an Agbased TCC coating for use as an EMI filter in PDP applications of thelike as discussed above, the FIG. 4 coating 30 including four layerstacks of ZnOx/Ag/NiCrOx sandwiched between metal oxides and nitrides.The FIG. 4 coating has different thicknesses than the coating of FIGS.1-3, and also in FIG. 4 the layers 3, 25, 26, 24, 43 from the FIG. 1-3embodiments have been removed. This shows that all layers in the FIG. 1embodiment are not essential, and some may be removed in certaininstances. This FIG. 4 coating 30 may have a sheet resistance less than1.5 ohm/sq and 1.0 ohm/sq measured as coated and after heat-treatment,respectively, in certain example embodiments, and a neutral transmissionin visible higher than 55% or 60% in certain example embodiments. Thesheet resistance can be further reduced through the trade-off oftransmission in visible by increased Ag thickness. If a lowertransmission is desired, the transmission can be reduced by increasedNiCrOx thickness and/or reduced x value. Metal oxides and nitridesshould have optical index in visible higher than 1.8, and can benonconductive such as SiNx or conductive such as ZnAlOx in differentexample embodiments. A multiple layer structure can also be used toreplace each metal oxide, nitride, or oxynitride, such as replacing TiOxby SiNx/TiOx or SnOx by SnOx/SiNx/ZnOx.

Referring to FIG. 5, a broad band visible antireflection (AR) coating50, such as the one described in FIG. 5 or any other suitable ARcoating, can be applied on the opposite surface of the substrate 1 (seeFIGS. 6-8) and/or laminated atop of the TCC 30 (see FIGS. 7-8) tofurther enhance the optical performance of the Ag based EMI protectioncoating 30 in certain example embodiments of this invention. Examples ofusing this Ag based TCC coating for display applications are shown inFIGS. 6-8. As explained above, the various FIG. 6-8 filter structuresmay be used in place of 100 or 100′ in the PDP device of FIG. 6 of US2006/0083938, in example applications of this invention. Note that inFIGS. 6-8, optional additional substrate(s) 1′, 1″ may be glass orplastic, and the glue may be any suitable adhesive or the like. Forexample, in one example, a TCC coating 30 having 4 layers of Ag (asshown in FIGS. 1( a), 3 and 4) is used as part of cover glass 1structure for outdoor display applications, and FIGS. 6-8 illustrateexample designs of this cover glass structure with the optionalpossibility of using it together with an AR coating 50. Opticalperformance of example is summarized in FIG. 9 when TCC 30 (e.g., seeFIG. 4, or FIG. 1) and AR (e.g., see FIG. 5) are coated on oppositesurfaces of the substrate 1. Transmission and reflection spectra detailsare shown in FIG. 10. As with other embodiments herein, the TCC EMIfilter coating 30 provides the following functions/advantages: reducesdamage from EMI radiation through highly conductive Ag layers, blocksignificant amounts of NIR and IR radiation from outdoor sunlight toreduce panel temperature, and enhances contrast ratio through reducedreflection.

Referring to FIGS. 11-13, another example of this invention is similarto the embodiments of FIGS. 1-10, but also includes an extra dye(es)based absorption layer(s) to reduce transmission at about 595 nm (asshown in FIG. 11) to improve color neutrality for plasma displayapplications. In certain example embodiments, the dye is for absorbingat selected wavelength ranges, but not other ranges. For example incertain example embodiments, the dye may absorb light proximate 595 nm(e.g., see FIG. 11) in order to improve color characteristics of PDPdevices. The dye inclusive layer (not shown) can be introduced into oneor more locations, such as between AR coating 50) and substrate (1), orbetween TCC 30 and substrate 1, or between TCC 30 and the glue layer, orembedded in the glue layer or substrate(s) 1 (see FIGS. 6-8). Theoptical performance of an example of this dye inclusive embodiment forPDP devices is shown in FIG. 12, and transmission and reflection spectraof an example of this embodiment are shown in FIG. 13. In this coverglass structure, the TCC coating 30 provides the following functions:block the emitting of EMI radiation from plasma panel by highlyconductive Ag layers, block NIR and IR radiation from sunlight to reducepanel temperature for outdoor usage, enhance contrast ratio throughreduced reflection, and block the emitting of NIR (850-950 nm) radiationfrom plasma panel to avoid the interference to nearby electronics.

FIGS. 14-19 are cross sectional views of EMI filters for display panels(e.g. PDP panels) according to other example embodiments of thisinvention. These embodiments may be heat treatable, and may be designedfor different sheet resistances (Rs). The EMI filter coatings of theseembodiments may be heat treated in a typical or conventional temperingfurnace, so that the glass substrate 1 is tempered when the coatedarticle is heat treated. Suitable black and/or silver frits can beapplied to and fired onto the coated surface with good adhesion and nosignificant damage to the coated surface.

FIGS. 14-19 are heat treatable (HT) versions and the coatings of theseembodiments can survive heat treatment at temperature of from about500-750 degrees C. (more preferably from about 520-650 degrees C.) whilestill maintaining an acceptable haze value following HT; and thecoatings of these embodiments can have a sheet resistance (Rs) of nomore than about 1.3 or 1.2 ohms/square (more preferably no more thanabout 1.0 or 0.90 ohms/square), and a visible transmission of at leastabout 60% (more preferably at least about 62 or 63%), following HT. Incertain example embodiments, the coated articles of these embodimentshave a haze value of no more than about 3 (more preferably no more thanabout 2.0 or 1.0) following HT. In the FIG. 14-19 embodiments, siliconnitride based layer(s) 3 and/or 3 a (and possibly 3 a′) may be Si-richas discussed above in certain example embodiments, and NiCr oxided basedlayer(s) 31 and/or 41 is/are only partially oxided in certain exampleembodiments. The use of such Si-rich silicon nitride and only partiallyoxiding at least one of the NiCrOx based layers results in a coatedarticle that is better able to withstand HT while maintaining suitablevisible transmission and haze values following HT. In certain exampleembodiments, NiCrOx based layer 41 is less oxided than are one, two orall three of NiCrOx based layers 11, 21 and/or 31. In certain exampleembodiments, one or both of NiCrOx based layer(s) 31 and/or 41 is/areless oxided than are one or both of NiCrOx based layer(s) 11 and/or 21;it has been found that this helps provide for a more heat treatablecoating with better thermal stability upon HT. In the FIG. 14-19embodiments, metal oxide (e.g., tin oxide) based layer 13 a (and 13 a′)is provided for improving adhesion between the silicon nitride basedlayer 3 a and zinc oxide based layer 17.

While the materials shown for the various layers in the drawings arepreferred materials in certain example embodiments of this invention,they are not intended to be limited unless expressly claimed. Othermaterials may be used to replace materials shown in the drawings inalternative example embodiments of this invention. Moreover, certainlayers may be removed, and other layers added, in alternativeembodiments of this invention. Likewise, the illustrated thicknessesalso are not intended to be limiting unless expressly claimed.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1. A display device comprising: a display panel; an electromagneticinterference (EMI) filter provided at a front portion of the displaypanel, the EMI filter including an EMI coating supported by a glasssubstrate, the EMI coating comprising the following layers moving awayfrom the glass substrate: a first dielectric layer; a first high indexlayer having a refractive index (n) of at least about 2.2; a first layercomprising zinc oxide; a first EMI shielding layer comprising silvercontacting the first layer comprising zinc oxide; a first layercomprising an oxide of Ni and/or Cr contacting the first EMI shieldinglayer comprising silver; a first metal oxide layer; a second layercomprising zinc oxide; a second EMI shielding layer comprising silvercontacting the second layer comprising zinc oxide; a second layercomprising an oxide of Ni and/or Cr contacting the second EMI shieldinglayer comprising silver; a second metal oxide layer; a third layercomprising zinc oxide; a third EMI shielding layer comprising silvercontacting the third layer comprising zinc oxide; a third layercomprising an oxide of Ni and/or Cr contacting the third EMI shieldinglayer comprising silver; an overcoat layer; and wherein the third EMIshielding layer comprising silver is thicker by at least 2 nm than thefirst EMI shielding layer comprising silver.
 2. The display device ofclaim 1, wherein the first high index layer comprises an oxide oftitanium.
 3. The display device of claim 1, wherein the glass substrateand the EMI coating combined have a visible transmission of at least55%, more preferably at least 60%.
 4. The display device of claim 1,wherein the third EMI shielding layer comprising silver is thicker thanboth the first and second EMI shielding layers comprising silver.
 5. Thedisplay device of claim 1, further comprising a second high index layerhaving a refractive index of at least 2.2, the second high index layercomprising an oxide of titanium and being located between the second andthird EMI shielding layers.
 6. The display device of claim 1, whereinthe panel is a plasma display panel, and wherein no high index layercomprising an oxide of titanium is located between the first and secondEMI shielding layers.